The use of plastic pipe has significantly increased in recent years. Normally, plastic pipe is produced by extruding molten plastic through a die orifice of an extruder. In order to change the diameter of the plastic pipe, it is usually necessary to change the die orifice of the extruder. This operation is labor intensive and requires to shut down the extruder. Furthermore, the process has the disadvantage of allowing only the production of pipe having discrete diameters such as 1", 2", 4", etc., but does not readily permit the production of pipe having any outside diameter specified by the customer.
Thus, it would be highly desirable to have a process available which allows the use of one die and, yet, permit the production of pipe having a plurality of diameters. Furthermore, it would be desirable to have such a process which allows the manufacture of plastic pipe having a diameter given by the customer.